The proposed research aims to combine the areas of speech understanding, binaural hearing, sound localization, and cochlear implants (CIs). The proposed research Is novel because it aims to understand the advantages, capabilities, and limitations of bilateral CIs under controlled multi-electrode stimulation and of more realistic auditory stiniuli that are modulated in time. Controlled multi-electrode stimulation research and research on binaural modulated stimuli has only started recently. Research on this topic Is a logical next |step in bilateral CI researx;h; moving to less controlled and more complex auditory stimuli. It would help provide understanding of an important advantage of bilateral Implantation, that of understanding speech in noisy environments. the main hypothesis driving this work Is that current CI systems introduce fundamental differences from [the Wealthy auditory system, and these differences alter important acoustic information enough to significantly diminish any binaural hearing advantage. These differences include, but are not limited to: interjaural tonotopic place mismatch, unequal interaural neural survival, varying loudness growth between indi\>idual electrodes and ears, channel interactions, partial or complete lack of interaural sound fusion, and lack;of travelling wave of an acoustic stimulus along the basilar membrane. Some of these limitations may be compensated by different processing schemes or changes to the physical devices. Other limitations are intrinsic to electrical stimulation and cannot be compensated with the current generation of CIs. The mentored phase of the proposed research focused on single-electrode binaural signal detection and sound localization. The independent phase of the proposed research will focus on multi-electrode binaural signal [detection, sound localization, and understanding speech in realistic listening environments. The ultimate aim is to provide a binaural advantage to bilateral CI users' ability to localize sounds and to understand speech in difficult listening environments, like noisy or reverberant rooms. This research has potential to guide the clinical implementation of a Unlfonn method of bilateral fitting of CIs.